Witnesses say thousands of Ukrainians fleeing violence in eastern Ukraine lined up late Thursday at a Russian border crossing in cars packed with personal belongings to cross into Russia.
The exodus, witnessed by an Associated Press reporter, came hours before a week-long Ukrainian cease-fire was to expire, with little progress reported in talks aimed at ending a deadly armed rebellion by pro-Russian separatists.
It remained unclear late Thursday whether Friday's 0700 UTC deadline will be extended.
Ukrainian border guards at the Izvaryne crossing late Thursday reported kilometers-long lines of cars seeking refuge in Russia. Earlier this week, Russian migration officials said more than 90,000 refugees had been registered on the Russian side of the border.
Russian officials were quoted as saying most of the evacuees said they were only temporarily relocating.
Hours earlier, Ukraine President Petro Poroshenko called on Russia to support his peace plan with “actions, not words." In an address to the Council of Europe, Mr. Poroshenko also accused Moscow of waging an “undeclared war” by backing and arming the separatists.
He also said that unless Russia returns Crimea, the Black Sea peninsula it annexed from Ukraine in March, normalization of bilateral relations is “impossible.”
Kerry calls on Russia
Earlier, U.S. Secretary of State John Kerry said it is "critical" for Russia "in the next hours" to call on pro-Russia separatists in Ukraine to disarm.
He made the call Thursday in Paris, after meeting with his French counterpart Laurent Fabius.
Kerry said he and the French foreign minister are in "full agreement" that Russian President Vladimir Putin must prove that Russia is working to persuade the separatists to disarm and become part of the peace process.
"We are in full agreement that it is critical for Russia to show in the next hours, literally, that they're moving to help disarm the separatists, to encourage them to disarm, to call on them to lay down their weapons and to begin to become part of a legitimate process,'' Kerry told reporters in Paris.
German Chancellor Angela Merkel telephoned Mr. Putin to make the same point. German and Russian accounts of the conversation quote Ms. Merkel as telling the Russian leader to demonstrate "in the coming hours" a strong commitment to ending support for the rebellion. Otherwise, she said, the European Union -- meeting Friday in Brussels -- will be forced to consider a new round of sanctions against Moscow.
The call took place “at the initiative of the German side” and touched on questions of “monitoring observance of the ceasefire between the sides in conflict, the necessity of extending the truce, the establishment of regular work by the contact group and the freeing of people being forcibly detained,” the Kremlin said.
OSCE monitors freed
Separately, the Organization for Security and Cooperation in Europe said four of its monitors, abducted by rebels last month, have been released. Aleksandr Borodai, the self-proclaimed "prime minister" of the breakaway Donetsk region, described the release late Thursday as a goodwill gesture.
Russia's RIA Novosti news agency quoted Borodai as saying he is confident four other monitors seized in late May will be released soon
On Wednesday, the Obama administration said it was ready to impose fresh sanctions on Russia if Moscow fails to take action to de-escalate the crisis in Ukraine.
The administration said it has delayed implementation as it presses for unified support from European and U.S. manufacturers for the measures.
White House spokesman Josh Earnest said Wednesday the new sanctions will target Russia's banking, energy and defense sectors.
The threat of new sanctions comes as American business leaders campaign against unilateral penalties, claiming they will hurt U.S. interests and cost American jobs.
The U.S. Chamber of Commerce and the Washington-based National Association of Manufacturers plan to stress the perceived threat to U.S. interests with a newspaper advertising campaign.
European leaders also have voiced concern that new sanctions could otherwise hurt Europe's expanding economic ties with Moscow. Still, they are expected to discuss possible new round at their summit in Belgium on Friday.
The European Union and the United States earlier imposed sanctions against specific Russian individuals and companies after Moscow annexed Ukraine's Crimean peninsula in March.
Pro-Russian fighters guard their military unit in the city of Donetsk, eastern Ukraine, June 27, 2014.
A just-released member of OSCE Special Monitoring Mission in Ukraine gets out of a vehicle next to Alexander Borodai, prime minister of the self-proclaimed Donetsk People's Republic, Donetsk, Ukraine, June 26, 2014.
A man sorts donated clothes at a former concert hall converted into a center for collecting humanitarian aid for refugees in Donetsk, Ukraine, June 26, 2014.
A man says goodbye to his relatives as they prepare to cross the border into Russia at the checkpoint in Izvaryne, Luhansk region, eastern Ukraine, June 26, 2014.
Pro-Russian separatists man a road checkpoint outside the town of Lysychansk in the Luhansk region of eastern Ukraine, June 24, 2014.
A coal miner walks at Privilnyanska coal mine damaged by shelling in the town of Pryvillya in Luhansk, Ukraine, June 24, 2014.
People block a car carrying Russian Ambassador in Ukraine Mikhail Zurabov and Ukrainian lawmaker Nestor Shufrich after a meeting with leaders of the self-proclaimed Donetsk People's Republic and Luhansk People's Republic in Donetsk, Ukraine, June 23, 2014.
People with their faces covered take part in a pro-Ukrainian anti-separatist rally near the Kyiv Pechersk Lavra, June 22, 2014.
An activist from a pro-Ukrainian radical youth group stands in a front of riot police outside the Russian embassy in Kyiv, June 22, 2014.
Riot police protect an office of the Russian Sberbank after people attacked it with the stones in Kyiv, June 22, 2014.
Some information for this report provided by Reuters and AP.